Ground wires: Do I have this right?

Question

I have 200A load center with a solid bare #6 ground wire tied to a ground rod. Ground/Neutral are bonded in the box.

Then run stranded #6 (does it have to bare?) to the 100A auto transfer switch. Ground/neutral are seperated. Ground bonded to box and neutral isolated. Do I also need a solid bare to ground rod? It’s right next to the 200A load center.

Next run stranded #6 (does it have to be bare?) to the 100A sub-panel down line from the transfer switch. Ground/neutral seperated. Ground bonded to box and neutral isolated. I do have a solid bare to ground rod here.

Can I use stranded between boxes? Does it have to be bare? Does each box have to tied to ground rod? Am I missing anything?

Thanks for your help guys.

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The meter box is connected to the 1st ground rod with #4 uninterrupted solid. The subpanel is connected to the meter box with #4 solid. They are back-to-back (the subpanel used to be the main panel). I have since isolated the neutral in the subpanel.

The NEW main panel is connected to its own ground rod with #4 solid. The neutral is bonded to ground.

1. Do I need to run ground between the NEW main panel and the subpanel? (Subpanel is currently grounded to the meter box)
2. Do I need to run ground from the NEW main panel and the transfer switch/ transfer switch to subpanel?
3. Do I need to run the transfer switch ground to the ground rod? (Neutral is isolated)

Answer 1

Ground wires between boxes can be solid or stranded. Most likely in wires this big, they will be stranded.

Grounds must be colored bare, green, or green/yellow. Those three "colors" are reserved for ground.

Answer 2

Is there already another ground running to the 100A sub panel? Are they located within the same structure? Why is there only one ground rod?

Under "ideal" conditions one 10' ground rod might pass when tested (with a $2500+ device almost nobody ever has or uses) so the standard is to install two 10ft X 5/8" ground rods spaced 6ft apart and connected with one continuous piece of #4 on the 200A service. Usually most local codes now just specify two separate ground rods because it's guaranteed to pass a long as it's wired properly. I don't know anyone with an AEMC 6240 besides large commercial electrical companies and they likely only have one they share.

Bonding the sub panel to the existing ground rods is accomplished through the separate #6 you're running with the two hots and 1 neutral to the sub panel. You can also bond to the existing ground rods (or install another one) for additional protection but you still must maintain the bonding between the main and sub panel.

Edit - just to clarify here, you're running the #6 copper ground wire with the other conductors in conduit or within the same feeder cable.